Intranet Usability Reports by Nielsen Norman Group (available for a price but none the less worth it)

• Intranet Usability Guidelines, vol. 1-10
• Intranet Portals
• Intranet Information Architecture (IA)
• Intranet Design Annuals: 2001 to 2009
• Financial Services Companies’ Intranets
• Technology Companies’ Intranets
• Knowledge-Intensive Companies’ Intranets
• Industrial and Manufacturing Companies’ Intranets
• Retail Companies’ Intranets
• Government Agencies/Public Sector Intranets

Intranet Usability Reports by Nielsen Norman Group